In an existing IGZO (indium gallium zinc oxide)-based AMOLED display device, when a TFT (thin film transistor) of a pixel unit driving circuit is subjected to a gate stress, a threshold shift will occur, which results in such a visual effect as image retention.
To be specific, as shown in FIG. 1, a 2T1C pixel unit driving circuit is taken as an example. Once a power source is turned off, scanning voltages Vscan1 and Vscan2 applied to a gate electrode of a first data input transistor T1 and a gate electrode of a second data input transistor T2 are decreased to 0V. The reason for the decrease is that the scanning voltage is usually generated by a charge pump and a capacitance for voltage stabilization is relatively small. In a normal case, data voltages Vdata stored in a first storage capacitor C1 and a second storage capacitor C2 are decreased rapidly to 0V, so there is no risk of gate stress at this time. However, in fact, the gate stress has been applied onto T1 and T2, and the threshold voltages of T1 and T2 have been increased. At this time, due to the voltage, i.e., 0V, applied to the gate electrodes of T1 and T2, T1 and T2 are in an off state, so charges are stored in C1 and C2 for a long period of time and cannot be released, even if no power is applied to the entire system. As a result, the gate stress is applied onto gate electrodes of a first driving transistor TFT1 and a second driving transistor TFT2 for a long period of time. When the display device is turn on again, due to the long-term gate stress applied onto the driving transistors after the previous shutdown, a user will find that there is the image retention on an AMOLED display screen for the last image before the previous shutdown. In FIG. 1, OLED represents an organic light-emitting diode, and ELVDD and ELVSS represent a high-level output end and a low-level output end of the driving power source, respectively.